Kinetic Molecular Theory (KMT) AKA: Kinetic Theory of Molecules (KTM)
KINETIC MOLECULAR THEORY
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Transcript of KINETIC MOLECULAR THEORY
KINETICMOLECULAR
THEORY
Kinetic Molecular Theory
A theory that explains the physical properties of gases by describing
the behavior of subatomic particles
Physical Properties of Gases:
• Gases have mass• Gases are easily compressed• Gases completely fill their containers•Gases diffuse rapidly•Gases exert pressure
KMT has 5postulates:
#1A gas consists of very small particles that
have mass. (molecules or atoms)
#2Gas particles are
very far apart from each other.
(therefore gases are easily compressed)
#3Gas particles are in continuous, rapid, random motion.
#4Collisions of gas
particles (with each other and with container) are perfectly elastic(no energy lost)
#5The average energy of the gas particles
depends on the temperature of the
gas.
We can measure gases in 4 ways:
Measurement UnitAmount of gas Moles
Volume (V) Liters (L)
Temperature (T) °C, °F, or K
Pressure (P) atm, kPa, Torr, mm Hg, or lb/in2
Temperature (T)
A measurement of the average
kinetic energy of a substance
Higher temperatures
cause gas particles to move
faster
K = C + 273
14C = ? K14C + 273 = 287K
To solve gas problems, the temp must always be
in Kelvin (K) !!!
Pressure (P)
The force per unit area on a
surface
Pressure is caused by gas particles
slamming into the container’s walls.
Units of Pressure:1) atmosphere (atm) 2) kilopascal (kPa)
3) millimeters of Mercury (mm Hg)4) Torr
5) Pounds per square inch (lb/in2)
1 atm = 101.3 kPa = 760 mm Hg = 760 torr = 14.7 lb/in2
STOP…collaborate and listen
Boyle’s Law
MUST BE AT CONSTANT TEMPERATURE!!
P1V1 = P2V21 = before2 = after
A gas occupies a volume of 0.458 L at a pressure of 1.01 kPa and temperature of 295 Kelvin. Although the temperature stays
the same, the volume is increased to 0.477 L. What is the new
pressure?
0.970 kPa
Charles’ Law
MUST BE AT CONSTANT PRESSURE!!
V1T2 = V2T1
1 = before2 = after
What will be the volume of a gas sample at 309 K if its
volume at 215 K is 3.42 L? Assume that pressure is
constant.
4.92 L
Gay-Lussac’s Law
MUST BE AT CONSTANT VOLUME!!
1 = before2 = after
2
2
1
1
T
P
T
P
A balloon with a pressure of 0.900 atm is heated from
105 K to 155 K. If volume is held constant, what is the new
pressure?
1.33 atm
Confused yet???There’s an
easier way…
Combined Gas Law
1 = before 2 = after2
22
1
11
T
VP
T
VP
JUST HOLD ONE QUANTITY CONSTANT!!(take it out of the equation)
The gas in a 0.010 L container has a pressure of 1.39 atmospheres. When the gas is transferred to a
0.017 L container at the same temperature, what is the pressure
of the gas?
0.82 atm
The gas inside a 70.8 mL piston has a temperature of
35.0°C. If the temperature is raised to 100.0°C, what is the
new volume of the gas?
85.7 mL
An elastic container is inflated to a volume of 18.0 liters at a pressure of 1.26 atm. The
container then expands to a new volume at a pressure of 1.05 atm.
What is the new volume?
21.6 liters
Avagadro’s LawEqual volumes of gas
(at same P and T) contain the same
amount of particles
1 mole = 6.02 x 1023 particles
Only works at same P and T
1 mole = 22.4 L
Ideal Gas LawThe mother of all gas
laws. It includes everything!
PV = nRT
P = pressure (atm)V = volume (L)n = moles (mol)
R = Gas ConstantT = Temperature
(Kelvin)
PV = nRT
KmolLatm0821.0R
MUST USE THESE UNITS!!!
PV = nRT
If the pressure exerted by a gas at 0.00°C in a volume of
0.0010 L is 5.00 atm, how many moles of gas are
present?
2.2 x 10-4 moles
Ideal gases don’t really exist…
…real gases do!
Real Gas
All gases are real gases.
DUH!!
Ideal Gas
A gas that is described by the KMT postulates.
Ideal Gas Law works most of the
time.
It does NOT work at very low
temperatures and very high pressures.
Dalton’s Law of Partial Pressures
The sum of the partial pressures
of the gases is equal to the total
pressure
Dalton’s Law of Partial Pressures
Ptotal = P1 + P2 + P3 + …
A balloon contains O2 and N2 gas. If the partial pressure of
the O2 is 0.75 atm and the partial pressure of the N2 is 0.55 atm, what is the total pressure of the balloon?
1.30 atm
The gas inside a 70.8 mL can contains H2O(g) and CO2(g) and has a total pressure of 760 mm Hg. If the partial pressure of the H2O is 350 mm Hg, what is the partial
pressure of the CO2?
410 mm Hg
Graham’s LawGases with smaller
masses move faster than gases with large masses
(like a kid in Walmart)
H2 moves faster than N2. Which of the following gases
moves the fastest?
O2
CO2
NH3
Cl2
I2
H2O
Ar
N2
Br2
STPStandard
Temperature and Pressure:
0C and 1 atm
How many moles of N2 gas are in a 4.5 L balloon at STP?
0.20 moles
A gas at STP is heated to 55°C. What is the new
pressure if volume is held constant?
1.2 atm
A gas tank contains CO2 and O2 gas. What is the total pressure in the tank if the
partial pressure of CO2 is 0.45 atm and the partial pressure
of O2 is 0.55?
1.00 atm